Constant current regulator with phase control switching means and de triggering means therefor

ABSTRACT

Current regulator device used for lighting circuits to control lamp brightness comprises a moving coil transformer having a main secondary winding connected to an illuminating load and an auxiliary secondary winding associated with the main secondary winding, and SCR phase control means connected to the auxiliary secondary winding for controlling the current therein and thereby the current in the main secondary winding and the load. The SCR control means are triggered by a transistor and pulse transformer circuit synchronized with the voltage from the alternating current supply which is rectified by a bridge circuit. A remote control circuit for operating the regulator to produce different brightness levels includes a plurality of parallel-connected transistor circuits having individually adjustable potentiometers.

United States Patent [72] Inventors Robert E. Babcock Hendersonville;Wayne R. Neal, Fletcher, both of N.C. [21] Appl. No. 837,014 [22] FiledJune 27, 1969 [45] Patented Sept. 28, 1971 [73] Assignee GeneralElectric Company [54] CONSTANT CURRENT REGULATOR WITH PHASE CONTROLSWITCHING MEANS AND DC TRIGGERING MEANS THEREFOR I 1 Claims, 3 DrawingFigs.

[52] [1.8. CI 323/6, 315/194, 315/278, 323/24, 323/34, 323/62 [51] Int.Cl G05f3/04 [50] Field ofSearch 315/194, 278; 323/6, 24, 34, 38, 48, 53,62

[5 6] References Cited UNITED STATES PATENTS 3,440,520 4/1969 Jonesetal.3,444,456 5/1969 Codichini Primary Examiner-William M. Shoop, Jr.

Assistant Examiner-A. D. Pellinen Attorneys-Sidney Greenberg, J. WesleyHaubner, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Currentregulator device used for lighting circuits to control lamp brightnesscomprises a moving coil transformer having a main secondary windingconnected to an illuminating load and an auxiliary secondary windingassociated with the main secondary winding, and SCR phase control meansconnected to the auxiliary secondary winding for controlling the currenttherein and thereby the current in the main secondary winding and theload. The SCR control means are triggered by a transistor and pulsetransformer circuit synchronized with the voltage from the alternatingcurrent supply which is rectified by a bridge circuit. A remote controlcircuit for operating the regulator to produce different brightnesslevels includes a plurality of parallelconnected transistor circuitshaving individually adjustable potentiometers.

owsiz SUPPLY NEG. POWER SUPPLY CONSTANT CURRENT REGULATOR WITH PHASECONTROL SWITCHING MEANS AND DC 'IRIGGERING MEANS THEREFOR The presentinvention relates to constant current regulators, and more particularlyto such regulators used in lighting circuits for supplying selectedlevels of current to lamps for controlling their brightness.

Among lighting circuits of the above type in which the invention mayadvantageously be employed are those used for lighting airport runwaysand in which the lamp brightness is controlled in accordance withvisibility conditions at the airport.

It is an object of theinvention to provide an improved constant currentregulator for electrical devices in which the current to the load may becontrolled to obtain desired power levels.

Itis a particular object of the invention to provide a constant currentregulator of the above type in a lighting circuit for controlling thebrightness of the lamps energized by the circuit.

Another particular object of the invention is to provide a currentregulator of the above type having a phase control semiconductorswitching device and triggering means therefor, wherein the triggeringof the phase control device is synchronized with the supply voltage.

Still another object of the invention is to provide a current regulatorapparatus of the above type which incorporates a remote control circuithaving improved stability and adjustability.

Other objects and advantages will become apparent from the followingdescriptionand the appended claims.

With the above objects in view, the present invention in one of itsaspects relates to a current regulator device comprising, incombination, a moving coil constant current transformer having mainprimary and secondary windings, and having terminals connected to themain primary winding for connection to a source of alternating current,load means such as a lamp connected to the main secondary winding forenergization thereby at a substantially constant current, controlcircuit means associated with the main secondary winding for varying thelevel of constant current supplied to the lamp load means comprising anauxiliary secondary winding adjacent the main secondary winding, phasecontrol bilateral switching means connected to the auxiliary secondarywinding for controlling the current therein, rectifying means connectedto the phase control switching means for rectifying the alternatingcurrent output thereof, actuating circuit means connected to therectifying means and to the phase control switching means for triggeringthe operation thereof, and means connected to the main primary windingand to the rectifying means for synchronizing the operation of theactuating circuit with the voltage across the switching means.

The invention will be better understood from the following descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. I is a circuit diagram of a constant current regulator deviceembodying a synchronizing arrangement in accordance with the invention;

FIG. 2 is a circuit diagram of a modification of the synchronizingarrangement of the. FIG. 1 circuit; and

FIG. 3is a circuitdiagram of a remote control circuit constructed inaccordance with the invention which may be employedwith the constantcurrent regulator device shown in FIG. 1.

Referring now to the drawings, and particularly to FIG. 1, there isshown a circuit arrangement energizing at a constant current a load I,such as an illuminating means. The illuminating means may be constitutedby one or more lamps, such as incandescent, gaseous discharge orfluorescent lamps. The circuit includes a movable coil constant currenttransfonner 3 comprising a main primary winding 3a connected toterminals 2 of a source of alternating current and a main secondarywinding 3b across which load I is connected. In such a movable, coiltransformer 3, either primary coil 3a or secondary coil 3b may be mademovable on the core relative to the other. As well understood in theart, such a transformer is a variable, impedance device that provides aconstant output current to a range of load impedances throughout alimited variation in the primary supply voltage, and corrects anyvariations in output current by changing the variable impedance inseries with the load. In such a device, the output current is constantat a particular level depending on the structure of the core and coilsand the ampere-turn relationship of the coils. In the regulator circuitemployed in the invention, a control device is incorporated for varyingin stepless fashion the level of the constant output current which wouldotherwise be fixed. The control device as shown in FIG. 1 comprises anauxiliary secondary winding 4 adjacent main secondary winding 3b and infixed spatial relation thereto. Connected across auxiliary secondarywinding 4 is a controlled rectifier switching circuit 5 which serves toprovide a phase controlled currentof desired amount in winding 4 tothereby vary the ampere-tums of main secondary coil 3b, and thusresulting in the desired adjustment of the constant current supplied toload I. Controlled rectifier circuit 5 includes a paralleled pair ofoppositely poled controlled rectifiers 7 and '8, which are typicallysilicon controlled rectifieis (SCR) having control (gate) electrodes 7'and 8 by means of which the SCRs are rendered conductive forunidirectional flow of current when a signal pulse is applied to therespective control electrodes. A power semiconductor symmetrical switchcould be used to replace the two SCR's.

Control electrodes 7' and 8' are connected respectively to secondarywindings 9a, 9b of pulse transformer 9, of which the primary isarrangedin actuating circuit 23 described below. Transformer 9 serves to isolatecontrolled rectifier circuit 5 from the trigger pulse generating circuitdescribed below and to provide pulsesof the proper polarity and voltageto control electrodes 7' and 8'.

The signal generating or actuating circuit 23 for triggering theoperation of SCR switching circuit 5 comprises solid state semiconductorcomponents, as more fully disclosed below, to provide improved stabilityand reliability in the operation of the triggering means. To provideunidirectional current for energizing triggering circuit 23, full-waverectifying bridge I7 is connected in series with auxiliary secondarywinding 4 across SCR switching circuit 5. The negative output terminalof bridge 17 is grounded, as shown, and the positive output terminal isconnected by a current limiting resistor 32 to a voltage clamping device20 such as a Zener diode and to transistor 24 of trigger circuit 23.Transistor 24 is arranged with its base connected to bridge 17 by acurrent limiting resistor 29, its collector connected by a resistor 25to a separate positive power supply 18 and its emitter connected topulse transformer primary 9c and the common ground. Connected at itsbase to the collector of transistor 24 via resistor 30 is transistor 26,which is connected across capacitor II with resistor 31 in series withits collector. Resistor 25 limits the current to the collector oftransistor 24 and the base of transistor 26, and resistor 30 ensuresthat transistor 26 does not turn on while transistor 24 is conductive.Resistor 31 limits the collector current of transistor 26 which resultsfrom discharge of capacitor 11.

Capacitor 11 is connected in series with variable resistor 10 andprovides therewith an RC time constant network connected at one side topower supply 18 and at the other side to transformer primary 9c. In theillustrated embodiment, a switch S, which may be manually operated, isprovided for connecting capacitor 11 via terminal L to variable resistor10 which serves as a local control, or for alternatively connectingcapacitor 11 to the remote control circuit described below by movingswitch S in contact with terminal R, as seen in FIG. 3. Connected inseries discharge relation with capacitor 11 and transformer primary 9cunijunction transistor (UJT) 27 which has a first base (base two)connected via current limiting resistor 28 to the positive power supply18 and a second base base one) connected to transformer primary 9c.

Power to triggering circuit 23 is furnished by an auxiliary alternatingcurrent source having terminals 50 to which is connected the primary ofstepdown transformer 40. Connected in series with the secondary oftransformer 40 are positive power supply 18 and negative power supply19, each of which may be of well-known construction and need not bedescribed herein in detail. Circuit arrangements providing such supplycurrents of the respective polarities are disclosed, for example, in theGeneral Electric Company Transistor Manual, 7th edition, 1964, inChapter 10, e.g., FIG. 10.1. Alternatively, the desired positive andnegative currents could be derived simply from DC batteriesappropriately connected in the circuit. Power supply devices 18 and 19and a center tap on the secondary winding of transformer 40 areconnected to a common ground, as shown, to provide for independentoperation of the positive and negative power supplies. Positive powersupply 18 is connected by conductor 35 to triggering circuit 23 aspreviously described, and negative power supply 19 is connected viacurrent limiting resistor 33 to the junction of resistor 32 and Zenerdiode 20.

For the purpose of synchronizing the SCR trigger pulses with the SCRanode voltage there is provided a stepdown transformer 22 having itsprimary winding connected across supply terminals 2 and its secondarywinding connected at one side to SCR switching circuit 5 and at theother side to bridge 17 as shown. In effect, bridge 17 is thus arrangedin series with both secondary windings 4 and 22b and as a result itvectorially adds the two voltages thereof, and the resultant rectifiedvoltage, reduced by resistor 32, is applied to the base of transistor 24through current limiting resistor 29.

In the operation of the described circuit, on each half cycle of thealternating current input derived from auxiliary secondary winding 4,one of the controlled rectifiers 7 and 8 will have a positive anode andthe other a positive cathode. There fore, a control signal applied tocontrol electrodes 7' and 8' will place only one of the controlledrectifiers in a conduction mode on each half cycle. A delay in the pointin the alternating current input cycle at which the control signalimpulse is applied to render the rectifier conductive is known as phasecontrol.

In the operation of actuating circuit 23, transistor 26 is normallybiased on by virtue of its connection to positive power supply 18 andthus prevents capacitor 11 from becoming charged. When the input currentapplied by bridge 17 to the base of transistor 24 is sufficient, e.g.,about 50 microamperes, transistor 24 is turned on, thus turning offtransistor 26, and allowing capacitor 11 to charge through variableresistor until its voltage level reaches the switching voltage of UJT27, e.g., about 13 volts, at which time UJT 27 fires and dischargescapacitor 11 through the discharge loop which includes transformerprimary 9c. UJT 27 turns off when current from capacitor 11 drops belowthe required holding current, and there is thus provided a signal pulseof particular duration and time transmitted by transformer 9 alternatelyto the gate electrodes of SCRs 7 and 8. The controlled rectifier 7 or 8which has an anode positive with respect to its cathode will then betriggered into conduction by the pulse current applied to controlelectrode 7 or 8' and the voltage which has built up across thecontrolled rectifier falls substantially to zero. The controlledrectifier 7 or 8 then permits a finite amount of current to flow in theauxiliary secondary winding 4 for the remainder of that half cycle. Onthe next half cycle as the anode voltage becomes negative, thecontrolled rectifier 7 or 8 which was conductive becomes nonconductiveand no current is transferred to winding 4 until the signal generatingcircuit fires the other controlled rectifier. The time in the half cycleat which the rectifier is gated is adjustable by the level of resistance10.

Since the output of diode bridge 17 is always present except when thealternating current voltage applied thereto reverses value, i.e., atzero point, transistor 24 is always on except briefly at the zerovoltage value. Thus, transistor 26 is switched on onlyvat current zero,thereby synchronizing the charge on capacitor 11 with the voltage acrossSCR switching circuit 5.

In order to ensure that the bridge output voltage is reducedsufficiently to turn off transistor 24 (at zero point), negative powersupply 19 is connected as shown via resistor 33 and Zener diode 20 tothe bridge output so that the DC voltage thereof is forced to a slightlynegative value at the zero crossing of the applied alternating current.In this arrangement the Zener diode serves as an ordinary forward biaseddiode drop for the negative supply current. Thus, power supply 19,resistor 33 and Zener diode 20 constitute a simple voltage divider.Zener diode 20 serves, in addition, to limit the excursion of positivevoltage to a predetennined value e.g., I0 volts, which is compatiblewith optimum function of the transistors in actuating circuit 23.

In a typical regulator circuit of the described arrangement used forairport runway lighting, terminals 2 are connected to a voltage supplyof about 2400 volts a-c and transformer 22 steps down this voltage to230 volts a-c. Terminals 50 of the control circuit typically areconnected to a supply of 120 volts a-c, and positive and negative supplydevices 18, 19 provide about 20 volts output in their respectivepolarities.

As variable resistor 10 is varied from full resistance to minimumresistance, the current through coil 4 would, in the illustrativearrangement, vary from 0 amperes to about amperes, and the currentthrough load 1 would vary from about 6.6 amperes to about 2.8 amperes.

FIG. 2 shows a modification of the FIG. 1 circuit, wherein the output ofbridge 17 is derived only from transformer 22. As shown, both sides ofsecondary winding 220 are connected to the input terminals of bridge 17,and neither secondary winding 220 or bridge 17 are directly connected toSCR switching circuit 5 or auxiliary secondary winding 4 as in the FIG.1 arrangement. The modified circuit still provides the desiredsynchronization of SCR anode voltage and trigger pulses since the outputvoltage of transformer 22 bears a constant phase relationship to the SCRvoltage.

When a constant current regulator of the described type is used for suchapplications as an airport runway lighting where brightness levels ofthe lamps must be adjusted in accordance with visibility conditions, itis usually necessary or desirable to provide for quick and reliableadjustment of the lamp brightness from a remote location. FIG. 3 shows aremote control circuit arrangement using solid state semiconductorcomponents which may be combined with the circuits of FIG. 1 or FIG. 2.The remote control circuit includes an adjustable resistor orpotentiometer 36 connected at one side by conductor 38 to negative powersupply 19, its adjustable tap being connected by conductor 37 to aplurality of parallel-connected transistor circuits providing differentstages of brightness levels of the lamp load, and the other side ofpotentiometer 36 being connected to the transistor circuitry byconductor 39 e.g., the common ground lead. Conductors 37, 38 and 39 areas long as necessary to enable adjustable resistor 36 to be placed in aremote location such as the control tower for operating the regulatordevice at the desired distance. Shown in FIG. 3 are only the first andlast stages of the remote control circuit, designated stage I and stage4, but it will be understood that additional stages of like circuits maybe included therebetween, and typically a total of four such stages,each including a variable resistor as described below, would be employedin an airport runway lighting system of the abovedescribed type.

The first switch stage comprises transistor 43 connected at its base topositive power supply 18 via current limiting resistor 44 and having itscollector also connected to power supply 18 via variable resistor 45 anddiode 46. The emitter of transistor 43 is connected to ground viaresistor 47. Conductor 48 connects the collector of transistor 43 toremote control terminal R, to which switch contact S is moved to allowcontrol by the remote potentiometer 36. An auxiliary collector currentpath with resistor 49 is provided across variable resistor 45 to provideproper collector current value for optimum operation of transistor 43.Diode 46 serves to isolate the auxiliary collector current from thecharge path of capacitor ll. Resistor 51 in series with variableresistor 45 provides a minimum resistance in this branch to protecttransistor 43 from excessive current.

To control the operation of transistor 43 to change the brightness oflamp load 1, the base of transistor 43 is connected to negative powersupply 19 via remote potentiometer 36, with Zener diode 41 and currentlimiting resistor 42 being arranged in series therewith. By-applicationof negative current to the transistor base sufficient to equal or exceedthe positive current thereon, transistor 43 will turn off, with theresults described more fully below.

Stage 4 comprises a similar circuit in parallel with the stage 1 circuitand like components thereof are designated by corresponding numerals.

Zener diode 41 of stage 1 has a selected voltage level less than that ofZener diode 41a of stage 4, so that transistor 43a of the latter stagewill not be turned off at the same value of negative current. As will beunderstood, the corresponding Zener diodes in any intermediate stageswill have different values between those of stage 1 and stage 4, so thatthe transistors in successive stages may be turned off in sequence byadjustment of remote potentiometer 36 to obtain desired lamp brightnesslevels.

In the operation of the described circuit, when remote potentiometer 36is adjusted to provide sufficient resistance so that no negative currentpasses through Zener diode 41 (or any corresponding Zener diode of thecircuit) the transistors of all stages will be turned on by virtue ofthe positive current which is applied to the bases thereof.Consequently, transistors 43, 43a conduct the current to ground and nocurrent is applied to capacitor 11 for charging it. As a result, SCRswitching circuit 5, shown in FIG. 1, is not triggered and lamp load 1is therefore at full brightness level. In order to reduce the brightnessto the next lower level, stage 1 of the remote control circuit isactuated by adjusting potentiometer 36 to allow sufficient current toexceed the Zener level of Zener diode 41 but not sufficient to pass theZener diodes of subsequent stages. As a result, transistor 43 is turnedoff, so that positive current passes through variable resistor 45 andconductor 48 to capacitor 11. By suitable adjustment of variableresistor 45, the rate of charging of capacitor 11 and hence the amountof current available to lamp load 1 will be cor respondingly varied toreduce the lamp brightness to the desired level as explained above.

When potentiometer 36 is adjusted to provide sufficient negative currentto actuate both stages 1 and 4 (as well as any intermediate stages), allthe transistors will be turned off and capacitor 11 will be charged at acorrespondingly higher rate to provide for a corresponding reduction oflamp brightness to the minimum level.

Diode 52 arranged in parallel with Zener diode 41 serves to limitnegative current excursion to avoid damage to the transistor. Diode 53shown in stage 4 provides necessary isolation between the parallelstages. Resistor 42 in series with the Zener diode should be low enoughin value to provide current adequate to tumoff transistor 43 and toforward bias diode 52, and high enough to avoid drawing excessivecurrent, so as to allow the necessary negative current to flow tosucceeding stages of the circuit. Resistor 47 provides temperaturestability for the transistor and an increase in input impedance toafford optimum bias current.

Stepless adjustment of lamp brightness is obtainable with the describedremote control circuit, since the amount of negative current whichpasses the respective Zener diodes may be varied by suitable adjustmentof remote potentiometer 36, and such variation in small increments willcorrespondingly vary the amount of positive current diverted byoperation of transistor 43 to conductor 48 for charging capacitor 111.

Although not shown, means such as current transformers may be provided,if desired, in the main secondary circuit to monitor the load currenttherein for the purpose of operating such devices as an ammeter and anopen circuit voltage protector of known type.

While the described constant current regulator device has been disclosedparticularly with respect to its use in an airport lighting system, itwill be understood that it may also be found useful for control of otherlighting equipment or of other types of apparatus which it is desired tooperate at adjustable levels of constant current, as, for example,various types of heating devices. Moreover, the remote control circuitdescribed and shown herein may be found useful for application to othertypes of apparatus than the lighting systems described herein.

While the present invention has been described with reference toparticular embodiments thereof, it will be understood that numerousmodifications may be made by those skilled in the art without actuallydeparting from the scope of the invention. Accordingly, we wish to haveit understood that we intend herein to cover all such modifications asfall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. Current regulator device comprising, in combination, a moving coilconstant current transformer having main primary and secondary windings,and having terminals connected to said primary winding for connection toa source of alternating current, load means connected to said mainsecondary winding for energization thereby at a substantially constantcurrent, control circuit means associated with said main secondarywinding for varying the level of constant current supplied to said loadmeans comprising an auxiliary secondary winding adjacent said mainsecondary winding, phase control bilateral switching means connected tosaid auxiliary secondary winding for controlling the current therein,rectifying means connected to said phase control switching means forrectifying the alternating current output thereof, actuating circuitmeans comprising a unidirectional switching means connected to saidrectifying means and to said phase control switching means fortriggering the operation thereof, and means connected to said primarywinding and to said rectifying means for synchronizing the operation ofsaid actuating circuit with the voltage across said switching means.

2. A device as defined in claim 1, said synchronizing means including anauxiliary transformer having a primary winding connected to said mainprimary winding and a secondary winding connected tosaid rectifyingmeans.

3. A device as defined in claim 2, the secondary winding of saidauxiliary transformer being connected to said phase control bilateralswitching means.

4. Current regulator device comprising, in combination, a moving coilconstant current transformer having main primary and secondary windings,and having terminals connected to said primary winding for connection toa source of altemating current, load means connected to said mainsecondary winding for energization thereby at a substantially constantcurrent, control circuit means associated with said main secondarywinding for varying the level of constant current supplied to said loadmeans comprising an auxiliary secondary winding adjacent said mainsecondary winding, phase control bilateral switching means connected tosaid auxiliary secondary winding for controlling the current therein,rectifying means connected to said phase control switching means forrectifying the alternating current output thereof, actuating circuitmeans connected to said rectifying means and to said phase controlswitching means for triggering the operation thereof, and meansconnected to said primary winding and to said rectifying means forsynchronizing the operation of said actuating circuit with the voltageacross said switching means, said synchronizing means including anauxiliary transformer having a primary winding connected to said mainprimary winding and a secondary winding connected to said rectifyingmeans, said actuating circuit means comprising a capacitor and aresistance connected in series, and unijunction transistor means andpulse transformer means connected across said capacitor in seriesdischarge relation therewith, a unidirectional current supply ofpredetermined polarity connected to said series-connected capacitor andresistance and to said unijunction transistor means, a first transistorhaving its collector connected to said unidirectional current supply,and a second transistor connected across said capacitor and to saidcollector of said first transistor, whereby when said first transistoris turned off, said second transistor is turned on and bypasses currentaround said capacitor to prevent charging thereof, and when said firsttransistor is turned on by the output of said rectifying means, saidsecond transistor is turned off, allowing charging of said capacitor.

5. A device as defined in claim 4, and a second unidirectional currentsupply of opposite polarity connected to the output of said rectifyingmeans for forcing the same periodically to current zero for periodicallyturning off said first transistor and thereby controlling charging ofsaid capacitor in synchronism with the voltage across said switchingmeans.

6. A device as defined in claim 4, said phase control bilateralswitching means comprising controlled rectifier means connected acrosssaid auxiliary secondary winding and being nonnally nonconductive toblock current flow through said auxiliary secondary winding and havingcontrol electrode means to render it conductive in either directiondepending on the polarity of the alternating current supply, saidcontrol electrode means being connected to the secondary of said pulsetransformer means for triggering thereby.

7. A device as defined in claim 4, and remote control rneans foradjusting the current in said main secondary winding comprising acurrent control circuit including a transistor connected at its base tosaid unidirectional current supply and said resistance connected to saidunidirectional current supply in series with the collector of saidtransistor, said capacitor being connected to the junction of saidresistance and said transistor collector and to the emitter of saidtransistor, said capacitor and said resistance forming an RC timeconstant circuit, and means connected to said transistor for at leasepartially turning off the same for controlling the operation thereof andthereby the operation of the RC time constant circuit.

8. A device as defined in claim 7, said last mentioned means comprisinga second unidirectional current supply of polarity opposite that of saidfirst-mentioned unidirectional current supply and connected to the baseof said transistor.

9. A device as defined in claim 8, and an adjustable resistor connectedbetween said second unidirectional current supply and said transistorbase in series therewith.

10. A device as defined in claim 9, and at least another current controlcircuit comprising a second transistor and a second resistancecorresponding to and in parallel with said first-mentioned currentcontrol circuit, and a plurality of parallel-connected voltage limitingmeans of different voltage levels respectively connected to thetransistors of the first and second mentioned current control circuitsand in series with said adjustable resistor for sequentially turning oi?the respective transistors upon adjustment of said adjustable resistor,and current blocking means isolating said resistances in the respectivecurrent control circuits from each other.

11. A device as defined in claim 10, said resistances in said respectivecurrent control circuits being adjustable.

1. Current regulator device comprising, in combination, a moving coilconstant current transformer having main primary and secondary windings,and having terminals connected to said primary winding for connection toa source of alternating current, load means connected to said mainsecondary winding for energization thereby at a substantially constantcurrent, control circuit means associated with said main secondarywinding for varying the level of constant current supplied to said loadmeans comprising an auxiliary secondary winding adjacent said mainsecondary winding, phase control bilateral switching means connected tosaid auxiliary secondary winding for controlling the current therein,rectifying means connected to said phase control switching means forrectifying the alternating current output thereof, actuating circuitmeans comprising a unidirectional switching means connected to saidrectifying means and to said phase control switching means fortriggering the operation thereof, and means connected to said primarywinding and to said rectifying means for synchronizing the operation ofsaid actuating circuit with the voltage across said switching means. 2.A device as defined in claim 1, said synchronizing means including anauxiliary transformer having a primary winding connected to said mainprimary winding and a secondary winding connected to said rectifyingmeans.
 3. A device as defined in claim 2, the secondary winding of saidauxiliary transformer being connected to said phase control bilateralswitching means.
 4. Current regulator device comprising, in combination,a moving coil constant current transformer having main primary andsecondary windings, and having terminals connected to said primarywinding for connection to a source of alternating current, load meansconnected to said main secondary winding for energization thereby at asubstantially constant current, control circuit means associated withsaid main secondary winding for varying the level of constant currentsupplied to said load means comprising an auxiliary secondary windingadjacent said main secondary winding, phase control bilateral switchingmeans connected to said auxiliary secondary winding for controlling thecurrent therein, rectifying means connected to said phase controlswitching means for rectifying the alternating current output thereof,actuating circuit means connected to said rectifying means and to saidphase control switching means for triggering the operation thereof, andmeans connected to said primary winding and to said rectifying means forsynchronizing the operation of said actuating circuit with the voltageacross said switching means, said synchronizing means including anauxiliary transformer having a primary winding connected to said mainprimary winding and a secondary winding connected to said rectifyingmeans, said actuating circuit means comprising a capacitor and aresistance connected in series, and unijunction transistor means andpulse transformer means connected across said capacitor in seriesdischarge relation therewith, a unidirectional current supply ofpredetermined polarity connected to said series-connected capacitor andresistance and to said unijunction transistor means, a first transistorhaving its collector connected to said unidirectional current supply,and a second transistor connected across said capacitor and to saidcollector of said first transistor, whereby when said first transistoris turned off, said second transistor is turned on and bypasses currentaround said capacitor to prevent charging thereof, and when said firsttransistor is turned on by the output of said rectifying means, saidsecond transistor is turned off, allowing charging of said capacitor. 5.A device as defined in claim 4, and a second unidirectional currentsupply of opposite polarity connected to the output of said rectifyingmeans for forcing the same periodically To current zero for periodicallyturning off said first transistor and thereby controlling charging ofsaid capacitor in synchronism with the voltage across said switchingmeans.
 6. A device as defined in claim 4, said phase control bilateralswitching means comprising controlled rectifier means connected acrosssaid auxiliary secondary winding and being normally nonconductive toblock current flow through said auxiliary secondary winding and havingcontrol electrode means to render it conductive in either directiondepending on the polarity of the alternating current supply, saidcontrol electrode means being connected to the secondary of said pulsetransformer means for triggering thereby.
 7. A device as defined inclaim 4, and remote control means for adjusting the current in said mainsecondary winding comprising a current control circuit including atransistor connected at its base to said unidirectional current supplyand said resistance connected to said unidirectional current supply inseries with the collector of said transistor, said capacitor beingconnected to the junction of said resistance and said transistorcollector and to the emitter of said transistor, said capacitor and saidresistance forming an RC time constant circuit, and means connected tosaid transistor for at least partially turning off the same forcontrolling the operation thereof and thereby the operation of the RCtime constant circuit.
 8. A device as defined in claim 7, said lastmentioned means comprising a second unidirectional current supply ofpolarity opposite that of said first-mentioned unidirectional currentsupply and connected to the base of said transistor.
 9. A device asdefined in claim 8, and an adjustable resistor connected between saidsecond unidirectional current supply and said transistor base in seriestherewith.
 10. A device as defined in claim 9, and at least anothercurrent control circuit comprising a second transistor and a secondresistance corresponding to and in parallel with said first-mentionedcurrent control circuit, and a plurality of parallel-connected voltagelimiting means of different voltage levels respectively connected to thetransistors of the first and second mentioned current control circuitsand in series with said adjustable resistor for sequentially turning offthe respective transistors upon adjustment of said adjustable resistor,and current blocking means isolating said resistances in the respectivecurrent control circuits from each other.
 11. A device as defined inclaim 10, said resistances in said respective current control circuitsbeing adjustable.